This invention relates to an artificial intraocular lens for insertion into the eye, for example to replace the natural lens after it has been removed because of injury or cataract.
A typical artificial intraocular lens (IOL) is fabricated of a clear, rigid, hydrophobic plastic material, usually polymethylmethacrylate (PMMA), to form an optical element with two curved faces. The IOL is typically implanted by inserting it via the same corneal or sclerotic incision used to remove the natural lens.
Conventionally, the IOL provides a single refractive power (for example, about +20 diopters) to focus images on the retina. The refractive power is determined by the relative indices of refraction of the eye's aqueous humor (1.34) and the lens material (1.50 in the case of PMMA) and the radii of curvature of the front and rear faces of the lens.
The IOL can be implanted either in the anterior chamber (located between the iris and cornea) or the posterior chamber (behind the iris). Because the IOL is typically both smaller and more dense than the natural lens, it must be held in place either by clipping it directly to the iris or suspending it by attachment fixtures, called haptics.
Various techniques have been proposed (a) to provide an IOL with a refraction power that can be changed to accommodate to distance or close-up viewing, (b) to render the IOL expandable to permit implantation of the contracted IOL via a small incision, and (c) to impart neutral buoyancy to the IOL.